As a type of antibacterial agents, polypeptide-based antibacterial agents comprising a polypeptide are known. Polypeptide-based antibacterial agents exhibit a wide antibacterial spectrum and some of them are known to exhibit antibacterial activity against bacteria resistant to other types of antibiotics. Examples thereof include magainin (Non-Patent Document 1), cathelicidin (LL-37) (Non-Patent Document 2) and Ovispirin-1 (Non-Patent Document 3) which are α helix antibacterial peptides. In addition to these, peptides having an antibacterial activity, such as defensins (Non-Patent Document 2) are known. Further, in recent years, novel α helix antibacterial peptides are created (Patent Document 1). However, their antibacterial activities are not sufficient when compared with those of the existing antibiotics. Thus, novel polypeptide-based antibacterial agents having a novel structure and an excellent antibacterial activity are continuously demanded.
Patent Document 2 suggests that polypeptides having a vascular endothelial growth activity also have an antibacterial activity. Patent Document 3 describes analogues of the polypeptides described in Patent Document 2, which have a particularly high antibacterial activity.